Method for improving a hardly soluble gelling agent

ABSTRACT

The present invention concerns a method for improving the solubility of gelling agents hardly soluble in water such as agar-agar, gelatin and carrageenan. Said method includes the step of contacting said gelling agent with a non-equilibrium plasma formed by applying a high frequency wave to a low pressure gaseous atmosphere, such as air, oxygen, carbon dioxide or nitrogen, and thereby obtaining a gelling agent readily soluble in water.

TECHNICAL FIELD

The present invention relates to a method for improving the solubilityof a gelling agent hardly soluble in water, more particularly to amethod for converting a gelling agent hardly soluble in water to onereadily soluble in water.

TECHNICAL BACKGROUND

As hardly soluble gelling agents, gelatin and agar-agar are generallyknown. For dissolving gelatin in water, first gelatin powder or gelatinsheet must be swollen with water then the mixture of gelatin and wateris heated. For dissolving agar-agar in water, on the other hand, theagar-agar must be heated in hot water and the temperature must bemaintained at at least 80° C. for a long time.

Under these circumstances, methods have been proposed and/or developedfor improving the solubility of gelatin, and the results of the researchconducted for this purpose have been reported.

Japanese Patent Publication No. 31,911/1973 and U.S. Pat. No. 3,362,830,for example, disclose methods including steps wherein gelatin powder isfirst dissolved in water together with an equivalent amount or more ofsugars, then the solution thus obtained is dried by means of suchmethods as spray-drying, etc. On the other hand, Japanese PatentDisclosure No. 162,949/1980 discloses a method wherein water-containinggelatin is heated by use of microwaves to melt and dry it rapidly, thenthe dried gelatin is frozen and subsequently it is crushed into powderin the frozen condition.

According to the former method, however, a large amount of sugars mustbe used as the quality-improving agent, and moreover, the resultinggelatin powder is a mixed powder of gelatin and sugars. Therefore itcannot be said that these methods improve the quality of gelatin itself.The latter method, on the other hand, indispensably requires the stepsof adding water for forming water-containing gelatin; drying forremoving the water content previously added thereto; and crushing thisdried gelatin in frozen condition, and thus the method is quitecomplicated.

On the other hand, no method for improving the solubility of agar-agarhas been proposed or developed so far at all.

DISCLOSURE OF THE PRESENT INVENTION

Under such circumstances as set forth above, the inventors of thepresent invention earnestly carried out research for developing a novelmethod for improving the solubility of hardly soluble gelling agentsincluding gelatin and agar-agar through very simple processes withoutadditionally using any improving agent such as sugar or the like. And asthe result, they have discovered that the solubility of a gelling agentcan be effectually improved by use of a non-equilibrium plasma.

The main object of the present invention is to provide a novel methodfor improving the functional characteristic of gelling agents such asgelatin and agar-agar, that is, a method for converting a gelling agenthardly soluble in water into a readily soluble gelling agent.

Another object of the present invention is to provide a gelling agentreadily soluble in water.

These objects and the other object of the present invention can beachieved by contacting the gelling agent with a non-equilibrium plasma.

The method of the present invention includes the steps of applying ahigh frequency wave irradiated to a low pressure gaseous atmosphere togenerate therein a non-equilibrium plasma, and contacting the gellingagent with the non-equilibrium plasma generated in this way.

Generally, a "plasma" is defined as the ionized gaseous condition formedwhen a substance absorbs an extremely high energy and therey saidsubstance is dissociated into electrified particles. Plasmas can roughlybe classified into equilibrium plasmas and non-equilibrium plasmas. Anequilibrium plasma is formed by electric discharge such as arc dischargeunder a relatively high gaseous pressure condition, whereas anon-equilibrium plasma, also called a "low temperature plasma", isgenerally formed under a low gaseous pressure condition. Accordingly,the temperature of a non-equilibrium plasma is lower than that of anequilibrium plasma. In the present invention, the latter, that is, anon-equilibrium plasma is used.

As the gas to be used for forming the non-equilibrium plasma, there canbe used, for example, air and oxygen. However, it is not necessary tolimit the gas to these, and any gas will do so long as it causes noproblem in view of food sanitation, and such gases as carbon dioxide,nitrogen, etc. may be used.

For forming the non-equilibrium plasma by using a gas such as thosementioned above, a publicly-known low temperature plasma-formingapparatus can be used in the present invention.

BEST MODE FOR PRACTISING THE PRESENT INVENTION

For treating the hardly soluble gelling agent (hereinafter referred tosimply as "the gelling agent") with the non-equilibrium plasma, thegelling agent is at first charged into a low temperature plasma-formingapparatus. In this instance, the gelling agent is spread on a tray as auniform layer, which is then placed in the plasma-forming apparatus, orthe gelling agent is place in a plasma-forming apparatus equipped withan agitator. Thus effective contact between the gelling agent and thenon-equilibrium plasma can be secured. However, it should be understoodthat in the present invention, other methods for contacting the gellingagent and the non-equilibrium plasma can be used.

After the gelling agent is charged in the low temperature plasma-formingapparatus, the pressure within the plasma-forming apparatus is reducedto a specific value, and subsequently, a high frequency wave is appliedto the low pressure gas within the plasma-forming apparatus. Applicationof the high frequency wave can be effected during introduction anddischarge of a suitable gas.

The pressure within the plasma-forming apparatus is lower than 100 torr,preferably lower than 20 torr.

Whether the non-equilibrium plasma is formed or not can be confirmed byluminescence accompanying formation of plasma.

The length of time for the contact between said non-equilibrium plasmaand said gelling agent differs depending on the output of the highfrequency wave, the kind of gas used, the degree of pressure decrease,and the type and amount of the gelling agent to be treated, but issufficient if within 180 minutes, preferably 5-60 minutes.

According to the method of the present invention, the solubility of thegelling agent itself can simply and readily be improved, and the gellingagent thus treated has substantially improved water-solubility ascompared with untreated gelling agents.

Hereinafter, we explain the present invention more concretely referringto non-restrictive Examples and comparative tests.

COMPARATIVE TEST

10 g each of agar-agar, gelatin, carrageenan powder were separatelyplaced as thin layers in a low temperature plasma-forming apparatus,whereafter the pressure within said low temperature plasma-formingapparatus was reduced to 0.5 torr. Subsequently high frequency wave of13.56 MHz at an output 300 W was applied within the apparatus and at thesame time oxygen was supplied to the apparatus at the flow rate 50ml/min. On the other hand, the pressure was maintained at 0.5 torr bymeans of a vacuum pump and thereby non-equilibrium plasma was formed.Under such conditions, the respective samples as mentioned above weretreated respectively for 5, 15, 30, 45, 60 and 180 minutes.

In order to determine the degree of solubility in hot water, theaforementioned 6 groups of samples, and also untreated agar-agar,gelatin and carrageenan powder as comparative samples, were dissolved inhot water and then cooled. The strength of the gel thus obtained wasmeasured according to the method explained below.

A gelling agent such as gelatin forms gel when it is swollen with water,dissolved by heating and then cooled. In other words, the gelling agentdoes not form gel unless it is dissolved in the water, and the greaterquantity dissolved, the higher strength of the gel formed, and this isthe reason that we measured the strength of the gel for confirming thesolubility of the gelling agent.

(i) Method for Dissolving Gelling Agent

(a) Agar-agar

A mixture of a 0.5 sample of agar-agar and 4.5 g sugar powder was put ina beaker. Then 50 ml boiling water was added thereto and said mixturewas agitated for 10 seconds. After leaving the mixture at roomtemperature for 15 minutes, it was cooled to 10° C., and 60 minuteslater, the gel strength was measured.

(b) Gelatin

A method similar to that described was carried out except that a 1 gsample of agar-agar and 4 g sugar were used and water of 30° C. was usedin place of boiling water.

(c) Carrageenan

A method similar to that described was carried out except that a 1 gsample of carrageenan and 4 g sugar were used and after adding boilingwater, the mixture was agitated for 30 seconds.

(ii) Method for Measuring Gel Strength

A plunger having a diameter of 10 mm was put into the gelled material atthe speed of 6 cm/min. and the load at the point when the gel collapsedwas measured in grams.

The results obtained according to the aforementioned methods are shownin Table 1.

                  TABLE 1                                                         ______________________________________                                        Plasma                                                                        Treatment Gel Strength (g)                                                    Time      Agar-agar    Gelatin Carrageenan                                    ______________________________________                                         0         54          3.9      3.2                                            5         96          10.1    19.1                                           15        127          10.4    23.8                                           30        147          10.4    40.3                                           45        152          9.6     47.8                                           60        164          8.6     54.0                                           180       141          5.8     53.3                                           ______________________________________                                    

As clearly shown by the numerical values in the column "Gel Strength" inTable 1, the agar-agar and gelatin treated according to the method ofthe present invention exhibited gel strengths about 2.5-3 times higherthan the values of untreated materials, and in case of carrageenan,about 7-18 times higher than untreated materials. This fact shows thatthe agar-agar, gelatin and carrageenan treated according to the presentinvention became more readily soluble in water by the degree that thegel strength was increased.

The above tendency was confirmed as well by visual observation. That isto say, when the respective sample solutions obtained in the abovecomparative test were observed by the naked eye, a large amount ofprecipitates was observed in the untreated sample solutions, whereasonly a very small amount of precipitates was observed in the samplesolutions treated according to the method of the present invention, andparticularly in case of the respective solutions of gelatin that wastreated for 15 minutes and agar-agar and carrageenan that were treatedfor at least 30 minutes, precipitates could hardly be observed.

Thus, according to the present invention, a hardly soluble gelling agentcan be converted into a readily soluble gelling agent without using oradding any improving agent by the simple method of contacting thegelling agent with a non-equilibrium plasma.

EXAMPLE 1

After placing 100 g of agar-agar powder in a thin layer in a tray withina low temperature plasma-forming apparatus, the pressure of saidplasma-forming apparatus was reduced to 0.2 torr. Subsequently,microwaves of a frequency of 2450 MHz and a power of 1 Km were appliedthereto and at the same time air was supplied to the apparatus at theflow rate 200 ml/min. Thus with the pressure maintained at 0.2 torr byuse of a vacuum pump, a non-equilibrium plasma was formed. The agar-agarpowder was kept within said plasma-forming apparatus for 15 minutes soas to contact it with the non-equilibrium plasma formed under the aboveconditions. Then application of microwaves, supply of air and pumpingwere stopped, and the pressure within said plasma-forming apparatus wasrestored to normal pressure and the agar-agar powder treated with thenon-equilibrium plasma was taken out.

The agar-agar powder thus obtained was found to be improved insolubility to boiling water.

EXAMPLE 2

After placing 100 g of gelatin powder in a thin layer in the tray withina low temperature plasma-forming apparatus, the pressure of saidapparatus was reduced to 5 torr. Subsequently, microwaves of a frequencyof 2450 MHz were applied at a power of 1 Kw and at the same time air wassupplied to the apparatus at the flow rate 200 ml/min. On the otherhand, the pressure within the apparatus was maintained at 50 torr by avacuum pump, and thereby a non-equilibrium plasma was formed. The plasmathus formed and the gelatin powder were kept in contact for 10 minutes.Subsequently the application of microwaves, air supply and vacuum pumpwere stopped, and after the pressure within the low temperatureplasma-forming apparatus had returned to normal, the gelatin powdertreated with the non-equilibrium plasma was taken out. To the gelatinpowder thus obtained, 45 g sugar was added, and further suitable amountsof a coloring agent, flavoring agent and souring agent and 200 ml ofwater at 30° C. were added and the mixture was agitated. Afteragitation, the mixture was poured into a jelly cup and cooled to 5° C.and kept at this temperature for 30 minutes to obtain a jelly.

EXAMPLE 3

After spreading 100 g of carrageenan powder over a tray within a lowtemperature plasma-forming apparatus, the pressure within the apparatuswas reduced to 0.5 torr. Subsequently microwaves of a frequency of 2450MHz were applied at a power of 1 Kw and at the same time air wassupplied at the flow rate 250 ml/min. On the other hand, the pressurewithin said apparatus was maintained at 0.5 torr by use of a vacuum pumpand thereby a non-equilibrium plasma was formed. The plasma thus formedand the carrageenan powder were kept in contact for 15 minutes. Then theapplication of microwaves, air supply and said vacuum pump were stopped,and after the pressure within the apparatus had returned to normal, thetreated carrageenan powder was taken out. To 3 g of the carrageenanpowder thus produced, 47 g sugar and suitable amounts of a coloringagent, flavoring agent and souring agent were added, and afterthoroughly blending the mixture, 100 ml of boiling water was addedthereto and the mixture was agitated, whereafter 100 ml cold water wasadded and agitation was continued further. Subsequently the mixture thusobtained was poured into a jelly cup, and cooled to 5° C. and maintainedat this temperature for 30 minutes to obtain a jelly.

EXAMPLE 4

After placing 100 g of agar-agar powder in a thin layer in a tray withina low temperature plasma-forming apparatus, the pressure within the lowtemperature plasma-forming apparatus was reduced to 5 torr. Oxygen gaswas supplied to the apparatus at the flow rate 50 ml/min and at the sametime the pressure within the apparatus was maintained at 5 torr.Subsequently microwaves of a frequency of 2450 MHz were applied at apower of 1 Kw, whereby non-equilibrium plasma was formed. The agar-agarpowder was retained within said plasma-forming apparatus for 120minutes, and it was contacted with said non-equilibrium plasma formedunder the aforementioned conditions. Then the application of microwaves,oxygen gas supply and the vacuum pump were stopped, and after thepressure within said low temperature plasma-forming apparatus hadreturned to normal, the agar-agar powder treated with non-equilibriumplasma was taken out. The agar-agar powder thus obtained was improved toa product excellent in solubility in boiling water.

While the invention has been particularly shown and described inreference to preferred embodiments thereof, it will be understood bythose skilled in the art that changes in form and detail may be madetherein without departing from the spirit and scope of the invention.

We claim:
 1. A method of improving qualities of a hardly soluble gellingagent which comprises contacting said gelling agent for a time period ofless than 180 minutes with a non-equilibrium plasma which is generatedunder a reduced pressure of lower than 100 Torr. in a gas selected fromthe group consisting of air, nitrogen gas, oxygen gas and carbon dioxidegas by applying a high frequency wave.
 2. The method of improvingqualities of a hardly soluble gelling agent according to claim 1 whereinsaid gelling agent is selected from the group consisting of agar-agar,gelatin and carrageenan.
 3. The method of improving qualities of ahardly soluble gelling agent according to claim 1 wherein said pressureis lower than about 20 Torr.
 4. The method of improving qualities of ahardly soluble gelling agent according to claim 1 wherein said timeperiod is in the range of from about 5 minutes to about 60 minutes.
 5. Agelling agent readily soluble in water prepared in accordance with themethod of claim 1.